1. Field of the Invention
This invention relates to bank-to-turn pursuit controllers for fixed wing aircraft and missiles, and more particularly, to such a pursuit controller capable of providing rapid and precise pursuit steering control for substantially lift supported vehicles operating in the presence of a gravitational field.
2. Description of the Prior Art
Present bank-to-turn pursuit controllers for fixed wing aircraft and missiles use ad hoc corrections to compensate for gravitational influence. These consist of "gravity bias" and "up elevator" corrections applied within the controller. Total lift load factor is limited by a saturation element in the command path. Bank angle commands are developed in a manner that bank angle motion of the aircraft interacts in an intimate way with the bank angle and lift load factor commands generated by the pursuit controller.
The nature of the above features limits the utility of the present bank-to-turn pursuit controllers to applications wherein vertical path angles are modest (e.g., .+-.30 degrees), wherein bank angles used are modest (e.g., .+-.60 degrees), and wherein the angular separation between the aircraft direction of travel and the direction of the target point is modest (e.g., .+-.30 degrees).
Consequently, therefore, a need exists for a large angle, gravity compensated bank-to-turn pursuit controller.
It is therefore an object of the present invention to provide a bank-to-turn pursuit controller which is effective for essentially all vertical path angles except zenith and nadir.
It is a further object of the present invention to provide a bank-to-turn pursuit controller capable of utilizing the full range of aircraft bank angles.
It is a further object of the present invention to provide such a bank-to-turn pursuit controller which is equally effective for pursuit steering toward a target point with direction substantially different from the vehicle direction of travel as well as toward a target point which is in a direction nearly the same as the vehicle direction of travel.
It is a still further object of the present invention to provide a bank-to-turn pursuit controller which eliminates the need to use negative lift and which uses no more positive lift than an amount selected as an upper limit.
It is a still further object of the present invention to provide such a bank-to-turn pursuit controller which provides precise compensation for gravitational influence upon the lift magnitude and orientation required for pursuit steering and which provides commands to rotate the vehicle direction of travel toward the target point in a systematic manner at every instant of time.
Other objects and advantages of the present invention will become apparent as the description thereof proceeds.